The present invention relates to a network telephone system for replying to a phone call to a subscriber which originates from another subscriber while the subscriber is communicating via a network such as Internet using a phone line.
There are listed below some abbreviations for use in this specification, which are typically used in the communications field. These abbreviations are suitably utilized for explanation throughout this specification.
PC . . . Personal Computer
ICW . . . Internet Call Waiting
IP . . . Internet Protocol
PSTN . . . Public Switched Telephone Network
TN . . . Telephone Network
LS . . . Local Switch
ISP . . . Internet Service Provider
GW . . . Gateway
CA . . . Call Agent
AS . . . Access Server
STP . . . Signal Transport Point
SCP . . . Service Control Point
DHCP . . . Dynamic Host Configuration Protocol
QoS . . . Quality of Service
DNS . . . Domain Name System
WWW . . . World Wide Web
FTP . . . File Transfer Protocol
URL . . . Uniform Resource Locator
IAM . . . Initial Address Message
Recently, a greater number of users receive a variety of services by using dial-up connection via a modem from a PC (Personal Computer). One of the services is an ICW (Internet Call Waiting) service. The ICW service is a service in which when a subscriber A receives a phone call from another subscriber B while being in dial-up connection to the Internet, the subscriber A is notified that there is an incoming call from the subscriber B via the Internet using IP packets, instead of sending an audible signal to subscriber via the phone line, and if the subscriber A replies, the connection for the call is established via the Internet.
FIG. 20 is a block diagram schematically showing a network for providing the conventional ICW service. FIG. 21 is a diagram showing a procedure of the conventional ICW service from the time when the subscriber A makes dial-up connection to the Internet to the time when starting conversation with another subscriber B.
Firstly, the subscriber A makes a call to an AS (Access Server) of an ISP (Internet Service Provider) of which the subscriber A is a member to effect dial-up connection, and log in a network for the ISP. Thereby, an IP (Internet Protocol) address from the ISP is assigned to the subscriber A.
Next, the ISP registers the IP address assigned to the subscriber A in an ICW server operated by the ISP. Also, the ISP makes a setup to transfer a phone call to the subscriber A who is in connection to the Internet to the ICW server. For example, the ISP makes a setup to call a specific telephone number which is prepared for a call transfer request, and transfer phone calls to the subscriber A to the ICW server. Thereafter, a call transfer process is performed automatically through a common channel signaling network.
In this way, after the ICW server has made various setups, if the subscriber B makes a call to the subscriber A who is connecting to the Internet, the call to the subscriber A is transferred to the ICW server under the control of the common channel signaling network. Then, the ICW server sends a message in IP packets notifying that there is an incoming call to the subscriber A via the Internet, using the registered IP address of the subscriber A. This message includes several choices which the subscriber A can select, and a message screen containing these choices is displayed on a screen of the PC operated by the subscriber A. For example, a message screen containing the choices such as xe2x80x9ca. Take a call,xe2x80x9d xe2x80x9cb. Reject,xe2x80x9d xe2x80x9cc. Transferxe2x80x9d and xe2x80x9cd. Save as a voice mailxe2x80x9d is displayed.
The subscriber A takes a desired choice from among a plurality of choices contained in this message screen. For example, if the subscriber A makes a choice xe2x80x9ca. Take a call,xe2x80x9d the ICW server connects a call transferred from the subscriber B via the Internet to the subscriber A. Thereafter, the subscriber B can talk with the subscriber A via the IP network.
As the prior art for notifying or transferring a phone call from the subscriber B to the subscriber A, xe2x80x9cNetwork Telephone Systemxe2x80x9d as disclosed in Japanese Patent Laid-Open No. 10-322462 is well known.
By the way, the conventional ICW service described in the above had the following three problems.
A first problem is that since the conventional ICW service is one of the services provided by the ISP to which subscriber A has subscribed, the subscriber desiring an ICW service is necessary to connect via an ISP providing this ICW service to the Internet. This means that when the subscriber connects via other ISP to the Internet, the subscriber can not receive the ICW service. For example, an ICW service of an ISP to which the subscriber A has subscribed is enabled by registering an IP address of the subscriber to an ICW server corresponding to this ISP, but the registration process to the ICW server provided in the specific ISP can not be effected, when the subscriber connects via the other ISP to the Internet. Accordingly, when the subscriber A connects via the ISP not applied for the use of the ICW service or the ISP not practicing the ISP service to the Internet, the subscriber A can not use the ICW service.
A second problem is that if the subscriber A has a phone call from another subscriber B while the subscriber A is connecting to the Internet, the call is all transferred to the ICW server, and therefore even if the call is thereafter connected via the Internet, the service charge may not become cheap in some cases. For example, suppose that there are a number of access points to an ISP across the nation, to which the subscriber A living in Nagoya has subscribed, an ICW server corresponding to this ISP is located in Tokyo. If the subscriber A has a phone call from the subscriber B who lives in Osaka while the subscriber A is connecting via an access point of Nagoya where the subscriber A lives to the Internet, the call from the subscriber B is once transferred to the ICW server in Tokyo. Therefore, if the subscriber A and the subscriber B subsequently make communication via the Internet, it follows that the subscriber B makes the long distance call to Tokyo, so that the telephone charge is more expensive than when directly calling the subscriber A in Nagoya without the Internet.
A third problem is that the link to the conventional PSTN (Public Switched Telephone Network) is difficult to make. When the subscriber A takes a call from the subscriber B while connecting to the Internet, the subscriber A is connected via the Internet at any time, and can not talk via the PSTN only. Particularly, the Internet has unstable quality of speech because the traffic is burst. Accordingly, for an important matter, the subscriber may want to talk by connecting the line not via the Internet, but only via the public switched telephone network which is conventionally provided. However, with the conventional ICW service, the link to the PSTN is difficult. Therefore, when the subscriber wanted to talk via the PSTN, the subscriber A once disconnected dial-up connection to the Internet, and then one of the subscribers A, B needed to call the other person again, which took much time and labor.
The present invention has been achieved in the light of these respects, and it is an object of the invention to provide a network telephone system which allows the use of a telephone service via the Internet, irrespective of whichever ISP may be used or without making dial-up connection (in this case, replying way is only via the IP network). It is another object of the invention to provide a network telephone system which can reduce the charge for telephone call when the subscriber makes communication via the Internet. Further, it is a further object of the invention to provide a network telephone system which can readily establish the link to the conventional PSTN.
A network telephone system of the invention comprises service providing unit for providing a predetermined service via a predetermined network to a first subscriber who has made dial-up connection, subscriber information registration unit for registering subscriber information necessary to monitor a call to this first subscriber who has made dial-up connection to the Internet, incoming call detection unit for detecting that there is an incoming call from a second subscriber to the first subscriber who is accessing an IP network such as the Internet via a dial-up connection to the service providing unit by monitoring a call incoming to the first subscriber on the basis of the subscriber information registered in the subscriber information registration unit, incoming call notification unit for notifying the first subscriber that the incoming call has been detected by the incoming call detection unit, and call control unit for controlling the call setup for voice between the first subscriber and the second subscriber, upon an instruction from the first subscriber who has received a notification by the incoming call notification unit. In this way, since a registration process for the subscriber information by the subscriber information registration unit is performed to a telephone service carrier upon a request from the first subscriber desiring the call to be transfer via IP network, the registration process can be effected, even if the first subscriber who has issued this request uses any Internet service provider, so that an incoming call from the second subscriber can be transferred to the first subscriber.
The subscriber information includes a regular subscriber""s number which is given to the first subscriber in advance by the telephone service carrier, and IP address which is assigned by the Internet service provider. Usually, the subscriber gets different IP address from the ISP at every time of dial-up connection. Desirably, the incoming call detection unit monitors an incoming call originated from telephone network to the subscriber""s number corresponding to the first subscriber by monitoring the call set-up messages (such as IAM) received from the common channel signaling network, and the incoming call notification unit notifies the first subscriber designated by the IP address associated with the registered phone number. In this way, using the subscriber""s number (e.g., telephone number), an incoming call to the first subscriber from the second subscriber can be discriminated. Using the IP address which is registered in the information registration unit at every time of dial-up connection, it is possible to notify the first subscriber who is receiving some service from service providing unit through the dial-up connection that there is an incoming call from the second subscriber.
A terminal unit for the first subscriber desirably includes registration request unit for requesting the registration by sending the subscriber information to the subscriber information registration unit. Since using the terminal unit for the first subscriber having the registration request unit, the subscriber information necessary for registration is transmitted from this registration request unit, the subscriber information registration unit get subscriber""s address regardless of what method the subscriber access the IP network and not depending on which ISP the subscriber subscribed.
The network is preferably configured to include a first network accommodating the lines for the first and second subscribers and having a service quality which does not vary depending on the traffic volume and the number of hops in the path between the two subscribers with respect to the voice, a second network having a service quality which varies depending on the traffic volume with respect to the voice but the communication charge in the second network is pretty lower than the communication charge in the first network, and a plurality of protocol conversion unit, installed at a plurality of sites, for converting the protocol between the first and second networks. In this case, the call control unit desirably makes a call setup via the first and second networks. Since a voice signal on the first network which is transmitted from the second subscriber can be converted into a voice signal on the second network, using protocol conversion unit, it is possible to transfer a call from the second subscriber via the second network, while the first subscriber is accessing the second network using various kinds of services provided by service providing unit via the first network.
Also, the call control unit desirably designates the protocol conversion unit available which is located near the residential place of the second subscriber, and makes a call setup between the first subscriber and the second subscriber via this designated protocol conversion unit. Since the protocol conversion unit located near the residential place of the second subscriber is used, the communication charge can be reduced in the case where the communication charge is imposed in proportion to the distance between the first subscriber and the protocol conversion unit.
The call control unit desirably designates the protocol conversion unit near the residential place of the second subscriber, based on the second subscriber""s number which is included in the IAM message from common channel signaling network. The subscriber""s number having an area code can be used to readily discriminate the residential place of the subscriber, because a part of the subscriber""s number corresponds to the residential place of the subscriber.
The first network includes a common channel signaling network for controlling the call, and each of the incoming call detection unit and the call control unit is preferably connected to the signaling network. The use of the common channel signaling network facilitates an operation of detecting an incoming call to the first subscriber which is performed by the incoming call detection unit. Also, the call setup operation by the call control unit can be facilitated by instructing a call connection via the signaling network.
Preferably, the first network is a public switched telephone network, and the second network is an IP network including a public Internet. When the second subscriber makes a phone call to the first subscriber via the public switched telephone network while the first subscriber is connected to the Internet via a dial-up connection, the call from the second subscriber can be connected via the Internet to the first subscriber. As a result, the communication charge can be reduced, and the first subscriber has no need of providing extra telephone line to reply to a telephone call from the second subscriber when using the Internet.
The call control unit preferably makes connection between the first subscriber and the second subscriber, using a call via the first network but not via the second network, waiting for the first subscriber line which has been used in the dial-up connection to be released, when the first subscriber instructs a call setup not via the second network. Since the link between the first and second networks can be readily established, the first network with stable quality can be selected to reply, rather than the second network with less stable service quality (speech quality), thereby allowing the subscriber to reduce the time and labor.
The subscriber information registration unit preferably transmits a predetermined message to the first subscriber to monitor a response to the message, and when there is no response, deletes the subscriber information for the first subscriber from the registration to make the call transfer request invalid. Though the communication may be interrupted for some cause, the interrupted state of communication can be detected by investigating the presence or absence of a message transmission and a response, and an unnecessary call transfer request from the subscriber can be made invalid, so that the network resource can be effectively utilized.
The call connection unit (incoming call detection unit) preferably makes a call waiting service invalid temporarily prior to a call monitoring operation, when the first subscriber is a user of call waiting service. In the case where the call waiting service is used, a local telephone switch transmits a special audio signal to the first subscriber, when the first subscriber has a phone call from the second subscriber. In this case, the communication between service providing unit and the first subscriber who has made dial-up connection may be interrupted due to this special signal. Therefore, such interruption of communication can be avoided by making the call waiting service invalid in advance.